Currently, digital camera modules are included as a feature in a wide variety of portable electronic devices. Most portable electronic devices are becoming progressively more miniaturized over time, and digital camera modules are correspondingly becoming smaller and smaller. Nevertheless, in spite of the small size of a contemporary digital camera module, consumers still demand excellent imaging. The image quality of a digital camera is mainly dependent upon the optical elements of the digital camera module.
Aspheric lenses are very important elements in the digital camera module. An aspheric lens can easily focus an image on an imaging point, because the aspheric lens can attain different reflective refractive indexes by means of selected different materials and profiles. Therefore an aspheric lens can avoid many of the image-forming problems of spherical lenses. In addition, with a single aspheric lens, the number of lens pieces in the camera is minimized. Thus the camera can have a reduced size. Two or more aspheric lenses may be used in some cameras for high quality image forming. Contemporary aspheric lenses are made of plastic or glass. Plastic aspheric lenses are generally manufactured by way of injection molding. Though the cost of plastic aspheric lenses is relatively low, plastic aspheric lens generally provide low image-forming quality compared to glass aspheric lenses. This is because the transparency of the plastic used is lower than that of glass.
Glass aspheric lenses are generally manufactured by way of glass molding. However, such glass aspheric lenses often have a high degree of surface roughness, because the glass molding process is difficult to control. A molded glass aspheric lens should be polished smooth. Nevertheless, the polishing process is difficult to perform because the glass aspheric lens has at least one aspheric surface. Therefore, the overall cost of molding glass aspheric lenses is escalated.
What is needed is a process for glass molding which can overcome the above-described problems.